1. Field of the Invention
This invention relates generally to rotating type table rolls used in roll tables for transferring metal workpieces, particularly hot metal workpieces, in metal processing plants such as rolling mills. More particularly, this invention relates to a simple and inexpensive composite table roll construction having thermal expansion characteristics sufficient to eliminate thermal warping and distortion which may cause binding and "freezing" of the roll bearings, and which additionally will minimize internal stresses which tend to reduce the overall roll life of composite table rolls.
2. Description of the Prior Art
In modern metal rolling mills, there are a variety of differing rolling processes and procedures for producing finished and semi-finished metal products. Typically, heated ingots, (steel or aluminum, for example) are hot rolled through one or more roll stands to semi-finished products such as slabs, blooms, or billets, which are subsequently further hot rolled through one or more roll stands to finished or semi-finished products, such as plates, structural products, bars, rods, hot strip and the like. Such roll stands generally comprise at least one pair of rolls between which the hot metal workpiece is passed to reduce and/or shape the hot metal workpiece as desired. As utilized herein, the term "hot metal workpiece" in intended to mean any hot metal being processed whether it be an ingot, slab, bloom, billet, plate, shape, bar, rod, hot strip or the like.
In addition to the roll stands which are utilized to reduce the hot metal workpiece to the desired cross-sectional thickness and configuration, numerous roll tables are provided and utilized to feed, receive, handle, transfer and hold the hot metal workpiece before, during and after the hot rolling operation. For example, there are feed tables to feed the hot metal workpiece to the roll stand, roll-out tables to receive the hot rolled metal workpiece from the roll stand, reversing tables to receive and return the hot rolled metal workpiece back to the roll stand, cooling tables where the hot rolled metal workpiece is permitted to cool, with and without water cooling, conveyer tables for merely conveying the hot metal workpiece from one point to another, furnace roll tables which support and convey the hot metal workpiece through a heating furnace prior to, or intermediate of, the hot rolling operations, as well as other such roll tables.
Typically, such roll tables comprise a plurality of horizontally disposed and parallel cylindrical rolls which are adapted to support the hot metal workpiece across the upper, parallel, cylindrical edge surface of the rolls, and convey the hot metal workpiece as desired by virtue of the uniformly rotating rolls. Accordingly, most roll tables are provided with a drive means, such as a plurality of electric motors, for causing the rolls to rotate as desired to convey the finished or unfinished hot metal workpiece.
The rolls which are utilized to make up a roll table typically comprise a solid, one piece cylindrical roll, or a one piece arbor provided with a hard protective roll sleeve, rotatably mounted within a bearing at each end, with one end drivably secured to the drive means, such as an electric motor. The table rolls are horizontally positioned in a closely spaced parallel alignment, and are usually water cooled from the under side by a plurality of water sprays, or internally cooled by water passageways within the body or arbor of the roll.
Since it is normally intended that the hot metal workpiece be in motion while on the roll table, the table rolls are normally heated and cooled in a relatively uniform manner by virtue of the fact that the table rolls are in constant rotation thereby heating and cooling the circumferential surfaces in a rather uniform manner. Most prior art table rolls utilized for handling hot metal workpieces are designed to accommodate for any such axial thermal expansion that may result. However, should the hot metal workpiece become stalled while on a roll table, as does frequently happen, either intentionally or accidently for a variety of reasons, the rolls very quickly become heated in a non-uniform manner. Specifically, when a hot metal workpiece is stalled and sits motionless on the roll table for even a very short period of time, the top portion of the rolls become excessively heated, to create a significant thermal gradient from the top to the bottom portion of the rolls. If water cooling is continued, the thermal gradient can become even more excessive. Such non-axial thermal gradients within the rolls will cause the heated upper portions to expand significantly, while the bottom portions may in fact even shrink and contract. This excessive non-uniform expansion will normally cause the rolls to bow upward by virtue of the excessive expansion in the upper portions, with the result that the bowed distortion will cause the journaled ends of the rolls to bind-up within the bearings and even "freeze" within the bearings so that the rolls cannot thereafter be rotated. Such a situation may not only require rather time consuming corrective measures, such as removing the hot metal workpiece to permit the rolls to cool to a more uniform temperature, but may further require maintenance work on the bearings and/or rolls.